Insert type electromagnetic flowmeter

ABSTRACT

An electromagnetic flowmeter which is insertable within a pipe line conducting a fluid whose flow rate is to be measured. The flowmeter includes a flow-tube assembly of small radial thickness constituted by concentrically-arranged inner and outer tubes defining an annular region. This region is occupied by an electrostatic shield, a pair of oppositely-disposed flat coils contoured to conform to the curvature of the inner tube to establish a magnetic field in a direction mutually perpendicular to the longitudinal axis of the inner tube and to the axis of the electrodes installed thereon, and a magnetic shell surrounding the coils. The remaining space in the region is filled with a potting compound to seal the components therein.

[111 3,745,824 [4 1 July 117, 1973 INSERT-TYPE ELECTROMAGNETIC FLOWMETER[75] Inventors: Elmer I). Mannherz, Southampton; John S. Yard,Warminster, both of Pa.

[73] Assignee: Fischer & Porter Co., Warminster,

22 Filed: Sept. 14, 1971 21 Appl. No.: 180,430

OTHER PUBLICATIONS Magnetic Flowmeters, Fischer & Porter Catalog ClOD,September, 1967, pg. 2.

Primary ExaminerCharles A. Ruehl Attorney-Michael Ebert [57] ABSTRACT Anelectromagnetic flowmeter which is insertable within a pipe lineconducting a fluid whose flow rate is to be measured. The flowmeterincludes a flow-tube assembly of small radial thickness constituted byconcentrically-arranged inner and outer tubes defining an annularregion. This region is occupied by an electrostatic shield, a pair ofoppositely-disposed flat coils contoured to conform to the curvature ofthe inner tube to establish a magnetic field in a direction mutuallyperpendicular to the longitudinal axis of the inner tube and to the axisof the electrodes installed thereon, and a magnetic shell surroundingthe coils. The remaining space in the region is filled with a pottingcompound to seal the components therein.

8 Claims, 7 Drawing Figures INSERT-TYPE ELECTROMAGNETIC FLOWMETERBACKGROUND OF THE INVENTION This invention relates generally toelectromagnetic flowmeters, and more particularly to an improvedinsert-type flowmeter having a markedly reduced insertion loss.

Magnetic flowmeters are adapted to measure volume rates of those fluidswhich present difficult handling problems, such as corrosive acids,sewage, slurries, detergents, and the like. In a magnetic flowmeter, amagnetic field is generated which is mutually perpendicular to thelongitudinal axis of the meter pipe through which the fluid flows and tothe axis of the meter electrodes. Since the velocity of the fluid isdirected along the longitudinal axis of the pipe, the voltage inducedwithin the fluid will be perpendicular to both the velocity of thisfluid and the flux linkages of the magnetic field. Thus the meteredfluid constitutes a series of fluid conductors moving through themagnetic field. The more rapid is the rate of flow, the greater theinstantaneous value of the voltage established at the electrodes.

The standard magnetic flowmeter is provided with a flow tube having endflanges, whereby the flow tube may be interposed between adjoining linepipes of sub stantially the same diameter which conduct the fluid whoseflow is to be metered. The flanges of the interposed flow tube arebolted or otherwise secured to the flanges on the adjoining pipes in thefluid line.

In a magnetic flowmeter arrangement of the standard type, the flow tubeis subjected to the same pressure as the pipes in the line. The flowtube must therefore be of a material and thickness sufficient towithstand this pressure, even though the strength of the flow tube isunrelated to its measuring function. This design factor contributessignificantly to the cost of a standard meter.

A reduction in the cost of a flowmeter design may be effected by meansof an insert-type meter such as that disclosed in the 1968 patent toRohmann U.S. Pat. No. 3,406, 569, in which the meter, rather than beinginterposed between line pipes conducting the fluid to be measured, isinserted in a section of one of these pipes. In an insert meter of theRohmann type, the meter includes a flow tube having a constricted throatsection which is surrounded by an electromagnet including a pair ofmultilayer coils and a laminated iron core, similar to the electromagnetshown in the 1961 patent to Head U.S. Pat. No. 3,005,342.

The radial thickness of an insert meter of the Rohmann type isrelatively large, particularly in the throat region. In the insert meterdisclosed in the 1963 patent to Sasaki U.S. Pat. No. 3,108,474, in whichthe inserted tube is of a uniform diameter, the radial thickness isnevertheless large, mainly because of the space requirements imposed bythe multi-layer wire bundles of the electromagnet.

Inasmuch as the flow tube in a standard meter has the same diameter asthe fluid line pipes, the tube does not obstruct the flow of fluid,hence the flowmeter introduces no loss or pressure drop in the line.However, the standard flowmeter,which is relatively bulky, has otherpractical drawbacks, as mentioned previously. On the other hand, in aninsertion type of flowmeter of the type heretofore known, the relativelylarge radial thickness of such meters is such as to create a significantobstruction in the fluid path, hence such meters are responsible for alarge insertion loss or pressure drop. Thus the economic and otheradvantages gained by known insert-type flowmeters are to a degree offsetby their characteristic insertion losses.

SUMMARY OF THE INVENTION In view of the foregoing, it is the main objectof this invention to provide an insert-type flowmeter having a flow-tubeassembly adapted to fit within a line pipe conducting the fluid whoserate is to be measured, the assembly having a relatively small radialdimension and consequently a low insertion loss.

More particularly, it is an object of the invention to provide aninsert-type flowmeter of the above type which is so installed in thepipe section that pipe line pressure is imposed both on the interior andouter diameters of the flow-tube assembly, whereby the insert may bemade of low-cost materials since it does not have to contain pipe-linepressure as do existing magnetic flowmeters.

Also an object of the invention is to provide a flowmeter of theabove-described type, the flowtube assembly having a flange adapted tobe clamped between the flanges of adjoining pipes in the flow line forsupporting the flow-tube assembly within a section of one of the pipes.

Yet another object of the invention is to provide an insert-typeflowmeter that is reliable and accurate in operation and is neverthelessof inexpensive design.

Briefly stated, these objects are attained in a magnetic flowmeterhaving a flow-tube assembly of relatively small radial diameter formedby concentricallyarranged inner and outer tubes defining an annularregion. Placed within the annular region is a conductive layerencircling the inner tube to provide an electrostatic shield for thecomponents of the assembly, and a pair of symmetrically-arranged flatcoils contoured to conform to the curvature of the inner tube andadapted to establish a magnetic field mutually perpendicular to thelongitudinal axis of the assembly and to the axis of electrodesinstalled at diametrically-opposed positions on the inner tube. Alsodisposed in the annular region is a magnetic shell surrounding the coilsand spaced therefrom, the remaining space in the region being filledwith a potting compound to seal the components therein.

In one preferred embodiment of the invention, the inner and outer tubesare joined to a mounting flange which is adapted to be sandwichedbetween the end flanges of adjoining pipes in the flow line to supportthe flow-tube assembly within a section of one of these pipes. Theflange is provided with a tab extension serving to support a terminalbox, the terminals of which are connected to leads passing through theflange and going to the electrodes, the coils and the conductive layerdisposed within the annular region.

OUTLINE OF THE DRAWING For a better understanding of the invention aswell as other objects and further features thereof, reference is made tothe following detailed description to be read in conjunction with theaccompanying drawing, wherein:

FIG. I is a longitudinal section taken through one preferred embodimentof an insert-type magnetic flowmeter in accordance with the invention,the meter being installed in a pipe line conducting the fluid to bemeasured.

FIG. 2 is a transverse section taken in the plane indicated by line 22in FIG. 1;

FIG. 3 is a perspective view of the flowmeter removed from the pipeline;

FIG. 4 is an end view of the flowmeter shown in FIG.

FIG. 5 is a plan view of one of the flat coils before it is contoured;

FIG. 6 is a longitudinal section through another embodiment of aninert-type meter in accordance with the invention; and

FIG. 7 is a schematic diagram illustrating the operation of theflowmeter.

DESCRIPTION OF THE INVENTION Referring now to FIG. 1, there is shown aninserttype electromagnetic meter in accordance with the invention, themeter including a flow-tube assembly generally designated by numeral 10,which is supported by a mounting flange 11. The fluid whose rate is tobe measured, flows through a line including pipes 12 and 13, whoseadjoining ends are provided with flanges 14 and 15, respectively.

The flow-tube assembly is inserted within the end section of pipe 13,mounting flange ll of the meter being sandwiched between pipe flanges l4and 15 and being secured thereto by bolts 16. The radial diameter of theflow-tube assembly 10 is relatively small, so that it introduces arelatively minor obstruction in the flow passage, thereby minimizing thepressure drop and the insertion loss.

The position of flow-tube assembly 10 on mounting flange 11 and theouter diameter of the assembly relative to the inner diameter of thepipe, are such that the flow-tube assembly is coaxially disposed withinthe pipe 13, thereby admitting fluid into the annular passage betweenthe exterior of the flow-tube assembly and the inner surface of thepipe.

Thus, the flow tube has fluid pressure both on its inside and outside,and it need not withstand high differential pressures, but only thosewhich will be encountered across the flow device. Since it need notcontain the static pressure of the system, it can be of lightweight andinexpensive construction. Thus the inserttype flow tube offers greatflexibility in installation, for it can be fitted on any existing lines,as long as the flange size of the flow-tube assembly can be matched tothe pipe flange size.

Flow-tube assembly 10 ,as best seen in FIGS. 2, 3 and 4, is constitutedby a cylindrical inner tube 17 formed of a non-magnetic material such asreinforced fiber glass or nylon. The end of the inner tube is integralwith or cemented on a circular flange section 11A having an extensiontab llAe. Inner tube 17 is disposed concentrically within an outer tube23 of larger diameter to define an annular region within which theflowmeter electromagnet and its electrostatic shield are disposed. Outertube 23 is secured at its end to a flange section 118 having a tabextension llBe matching flange section 11A and extension llAe,respectively.

Installed on inner tube 17 at diametrically-opposed points thereon are apair of electrodes 18 and 19, only one of which is visible in FIG. 3,the electrodes being connected by leads 21 to a terminal box 22 mountedon tab extension "Be.

The electromagnet is constituted by a pair of flat spiral-wound coils 24and 25, which are contoured to conform to the curvature of the innertube 17. The coils are symmetrically mounted on the upper and lowerhalves of a thin sleeve 26, formed of asbestos or similar insulatingmaterial. The inner surface of sleeve 26 is plated, coated or otherwiseprovided with a layer 27 of electrically conductive material, such asaluminum or copper. This conductive non-magnetic layer functions toelectrostatically shield the fluid passing through the inner tube fromthe electromagnetic coils.

Surrounding coils 24 and 25 and spaced therefrom, is a magnetic shell 28made of iron or other ferromagnetic material. This shell provides acontrolled return path for the magnetic flux produced by the coils, theshell lying against the inner surface of the outer tube The leads 21from the electrodes, the wires from coils 24 and 25 and the ground wirefrom electrostatic shielding layer 27, are brought from the annularregion between the inner and outer tubes of the flowmeter assembly andpass as a bundle between the tab extensions llAe and llBe of the flangesections to the terminals in terminal box 22. After these connectionsare made, the two flange sections are joined together by a suitablebonding agent to creat the mounting flange 11 shown in FIG. 1. The airspace remaining in the annular region between the inner and outer tubesof the assembly is then filled with a suitable potting compound, such asan epoxy resin, to seal in the components and thereby isolate them fromthe field. Thus while all components of the meter are submerged in thefluid, they are protected therefrom.

In flange 1 1, the two lower holes 29 and 30 on the tab extension, aredesigned to receive the flange bolts 16 (FIG. 1), which join theflowmeter flange to the pipe flanges. These holes also serve to properlylocate flowtube assembly 10 within the pipe section. The single upperhole 31 on the tab extension of flange 11 is provided for liftingpurposes.

Referring now to FIG. 5, one of the coils, namely coil 24, is separatelyshown in plan view. It will be seen that the coil is spiral-wound inpancake style in a common plane and has a diamond configuration. Thusthe thickness of the coils is no greater than that of the wire toproduce a flat or planar form. When the coils are contoured to conformto the curvature of the inner tube, the coils assume a saddle-likeconfiguration. In practice, two layers may be used for the coils, theresultant coil still being quite flat.

The concentric arrangement of the components within the annular regionof the flow-tube assembly and the flat or planar coils therein, makespossible a compact assembly of small radial thickness. In practice, thisthickness may be in the range of one-half to fiveeighths of an inch in atwo-or-three foot diameter meter, thereby minimizing the insertion lossof the assembly.

It is also possible, as shown in FIG. 6, to place a flange l l at apoint displaced from the end of the flowtube assembly 10, such as at themidpoint of the assembly. In this instance, the flow-tube assembly, halfof which lies in pipe 12 and the other in pipe 13, is fabricated so thatits outer tube is formed by two pieces, each having an integral flangesection of one half the thickness of the completed flange. The innertube in this case, is without any flange.

Alternatively, the insert meter may be made entirely without flanges, inwhich case the flow-tube assembly is inserted into a pipe section andheld therein by grout, cement or the like. For this purpose, the variouswires from the components of the assembly are brought out through thepipe section by means ofa suitable water-proof cable. in order tomaintain a balanced pressure on both the inner and outer wall of theflow-tube assembly, openings are left in the grout at one end of theinsert.

The operation of the device is based on Faradays Law of electromagneticinduction. As shown in FIG. 7, the fluid to be metered passes throughthe inner tube 17 in the direction of the longitudinal axis X which ismutually perpendicular to the plane of the electrodes 18 and 19, and tothe plane Y of the electromagnetic field B established between coils 24and 25.

We shall consider a section of the metered fluid passing through theinner tube 16 as a conductor, the length of which is equal to thediameter of the inner tube. As the fluid moves transversely at velocityV through magnetic field B, a voltage E is induced across this sectionin the plane of the electrodes. This voltage is proportional to the rateof fluid flow. Expressed mathematically,

E l/C BVD; where c is a constant. Thus the insert meter functions in thesame manner as a standard magnetic flowmeter, but is much more compactand more easily installed.

While there have been shown and described preferred embodiments ofinsert-type electromagnetic flowmeters in accordance with the invention,it will be appreciated that many changes and modifications may be madetherein without, however, departing from the essential spirit of theinvention.

We claim:

I. An insert-type electromagnetic flowmeter, said flowmeter beingprovided with a flow-tube assembly of relatively small radial thicknessadapted to fit within a line pipe conducting the fluid to be metered,said flowmeter assembly comprising:

A. concentrically-disposed inner and outer tubes of uniform diameterdefining an annular region;

B. a pair of flat coils symmetrically disposed within said region aboutsaid inner tube and contoured to conform to the curvature thereof,

C. a magnetically -permeable shell surrounding said coils, said shellbeing adjacent the outer tube,

D. a potting. compound filling the remaining space in said region toseal in the components disposed therein, and

E. a mounting flange mounted at the end of said assembly, said flangebeing constituted by two joined sections, one of which is secured to theend of the inner tube and the other to the end of the outer tube, leadsfrom the coils being sandwiched protectively between the joinedsections.

2. A flowmeter as set forth in claim 1, wherein said inner and outertubes are fabricated of fiberglass.

3. A flowmeter as set forth in claim 1, wherein said flat coils areconstituted by a spiralwound layer having a diamond-shapedconfiguration.

4. A flowmeter as set forth in claim 1, further including a layer ofelectrically-conductive material interposed between said coils and saidinner tube to provide an electrostatic shield.

5. A flowmeter as set forth in claim 4, wherein said layer is formed onthe inner surface of an insulating sleeve surrounding said inner tube.

6. A flowmeter as set forth in claim 1, wherein said flange includes anextension tab, a connector box supported thereon, the leads from thecoils in said region passing between the sections of the flange to saidbox.

7. A flowmeter as set forth in claim 1, wherein the radial thickness ofsaid assembly is less than 1 inch.

8. A flowmeter as set forth in claim 1, wherein the outer tube of theflow-tube assembly is spaced from the inner surface of the pipe in whichthe assembly is inserted, to define an annular passage into which thefluid is admitted.

UNlTE-D STATESE ENT @DFICD CERTlFlCATE 0F CGRECTKGN Patent No. 4 DatedJuly 17; 1973 Column 2, line'22: "flowm" should have read flow- IWEMMQElmer D. Mannherz and John S. Yard It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

line 23 "eter" should have read meter m L line 31 "field" should haveread fluid Signed and sealed this 22nd day of January 197A.

( SEAL) Attest:

EDWARD M.FLETCHER, JR. RENE D. TEG'IMIEYER Attesting Officer ActingCommissioner of Patents

1. An insert-type electromagnetic flowmeter, said flowmeter beingprovided with a flow-tube assembly of relatively small radial thicknessadapted to fit within a line pipe conducting the fluid to be metered,said flow-meter assembly comprising: A. concentrically-disposed innerand outer tubes of uniform diameter defining an annular region; B. apair of flat coils symmetrically disposed within said region about saidinner tube and contoured to conform to the curvature thereof, C. amagnetically -permeable shell surrounding said coils, said shell beingadjacent the outer tube, D. a potting compound filling the remainingspace in said region to seal in the components disposed therein, and E.a mounting flange mounted at the end of said assembly, said flange beingconstituted by two joined sections, one of which is secured to the endof the inner tube and the other to the end of the outer tube, leads fromthe coils being sandwiched protectively between the joined sections. 2.A flowmeter as set forth in claim 1, wherein said inner and outer tubesare fabricated of fiberglass.
 3. A flowmeter as set forth in claim 1,wherein said flat coils are constituted by a spiral-wound layer having adiamond-shaped configuration.
 4. A flowmeter as set forth in claim 1,further including a layer of electrically-conductive material interposedbetween said coils and said inner tube to provide an electrostaticshield.
 5. A flowmeter as set forth in claim 4, wherein said layer isformed on the inner surface of an insulating sleeve surrounding saidinner tube.
 6. A flowmeter as set forth in claim 1, wherein said flangeincludes an extension tab, a connector box supported thereon, the leadsfrom the coils in said region passing between the sections of the flangeto said box.
 7. A flowmeter as set forth in claim 1, wherein the radialthickness of said assembly is less than 1 inch.
 8. A flowmeter as setforth in claim 1, wherein the outer tube of the flow-tube assembly isspaced from the inner surface of the pipe in which the assembly isinserted, to define an annular passage into which the fluid is admitted.